---
title: Jest
description: Learn how to use Jest in a Turborepo.
---

import { Callout } from '#/components/callout';
import { File, Folder, Files } from '#/components/files';
import { PackageManagerTabs, Tabs, Tab } from '#/components/tabs';
import { CreateTurboCallout } from './create-turbo-callout.tsx';

[Jest](https://jestjs.io/) is a common test runner with a vast ecosystem. Integrating with Turborepo will lead to enormous speed-ups.

<CreateTurboCallout />

## Setting up

Let's say we have a monorepo that looks like this:

<Files>
  <Folder name="apps" defaultOpen>
    <Folder name="web" defaultOpen>
      <File name="package.json" />
    </Folder>
  </Folder>
  <Folder name="packages" defaultOpen>
    <Folder name="ui" defaultOpen>
      <File name="package.json" />
    </Folder>
  </Folder>
</Files>

Install `jest` into the packages where you plan on having test suites. For this example, we will have tests in `web` and `@repo/ui`:

<PackageManagerTabs>
<Tab>

```bash title="Terminal"
npm install jest --workspace=web --workspace=@repo/ui --save-dev
```

</Tab>

<Tab>

```bash title="Terminal"
yarn workspace web add jest --dev
yarn workspace @repo/ui add jest --dev
```

</Tab>

<Tab>

```bash title="Terminal"
pnpm install jest --save-dev --filter=@repo/ui --filter=web
```

</Tab>
</PackageManagerTabs>

Both the `apps/web` and `packages/ui` have their own test suites, so we'll add a `test` script to their `package.json`:

<Tabs items={["web", "@repo/ui"]}>
<Tab value="web">
```json title="./apps/web/package.json"
{
  "name": "web"
  "scripts": {
    "test": "jest"
  },
  "devDependencies": {
    "jest": "latest"
  }
}
```
</Tab>
<Tab value="@repo/ui">
```json title="./packages/ui/package.json"
{
  "name": "@repo/ui"
  "scripts": {
    "test": "jest"
  },
  "devDependencies": {
    "jest": "latest"
  }
}
```
</Tab>
</Tabs>

Inside the root `turbo.json`, create a `test` task:

```json title="./turbo.json"
{
  "tasks": {
    "test": {}
  }
}
```

Now, `turbo test` can parallelize and cache all of the test suites from each package, only testing code that has changed.

## Running tests in watch mode

When you run your test suite normally, it completes and outputs to `stdout`. This means you can [cache it](/repo/docs/crafting-your-repository/caching) with Turborepo.

But when you run your tests in a watched mode, the process never exits. This makes a watch task more like a [development task](/repo/docs/crafting-your-repository/developing-applications).

Because of this difference, we recommend specifying **two separate Turborepo tasks**: one for running your tests, and one for running them in Jest's watch mode. Inside your each `package.json` file for each workspace:

<Tabs items={["web", "@repo/ui"]}>
<Tab value="web">
```json title="./apps/web/package.json"
{
  "name": "web"
  "scripts": {
    "test": "jest",
    "test:watch": "jest --watch" // [!code highlight]
  }
  "devDependencies": {
    "jest": "latest"
  }
}
```
</Tab>
<Tab value="@repo/ui">
```json title="./packages/ui/package.json"
{
  "name": "@repo/ui"
  "scripts": {
    "test": "jest",
    "test:watch": "jest --watch" // [!code highlight]
  },
  "devDependencies": {
    "jest": "latest"
  }
}
```
</Tab>
</Tabs>

Inside the root `turbo.json`:

```json title="./turbo.json"
{
  "tasks": {
    "test": {},
    "test:watch": {
      "cache": false, // [!code highlight]
      "persistent": true // [!code highlight]
    }
  }
}
```

You can now either run this task using [global `turbo`](/repo/docs/getting-started/installation#global-installation) as `turbo test:watch` or from a script in your root `package.json`:

<Tabs items={["Global turbo", "./package.json"]}>
<Tab value="Global turbo">

```bash title="Terminal"
turbo test
```

```bash title="Terminal"
turbo test:watch
```

</Tab>

<Tab value="./package.json">

```json title="./package.json"
{
  "scripts": {
    "test": "turbo run test",
    "test:watch": "turbo run test:watch"
  }
}
```

</Tab>

</Tabs>
